The Italian giants were facing Udinese on Saturday night when the shot-stopper was abused by the home fans.
Clearly upset by what he had heard, Maignan walked off the pitch after 31 minutes at the Stadio Friuli as he showed that he would not tolerate the abuse.
As well as being consoled by the Udinese players, AC Milan's stars followed the Feench goalkeeper off the pitch in solidarity with their teammate, leading to the game being temporarily suspended.
With the referee investigating what had happened by speaking to the matchday stewards and those around the ground, Maignan stood on the touchline, before making his way down the tunnel.
He was, again, followed and supported by his AC Milan teammates.
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The Italian giants confirmed what had happened on their social media channels, writing: "There is absolutely no place in our game for racism: We are appalled.
"We are with you, Mike."
After a lengthy stoppage in play, the match resumed with AC Milan holding a 1-0 lead thanks to Ruben Loftus-Cheek's goal.
But that lead was short-lived, with Udinese drawing the game level just before half-time through Lazar Samardzic.
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Things then got worse for Milan when Florian Thauvin gave Udinese a 2-1 lead following a defensive mix-up.
But goals from Luka Jovic and Noah Okafor ensured that AC Milan went home with the three points.